The soft attention model was proposed for machine translation problem in NLP [1]}, and Xu et al. [2]} extended it to image caption generation as the task is analogous to `translating' an image to a sentence. Specifically, they built a stochastic hard attention model with the aid of REINFORCE and a deterministic soft attention model. The two attention mechanisms were applied in image captioning task, with good results. Subsequently, Sharma et al. [3]} built a similar model with the soft attention applied in action recognition from videos.
